Packages of chip devices are built from several layers with different thermo-mechanical characteristics. During production, chip devices must pass different reliability stress tests, including several cycles of heating and cooling profiles. During such testing, chip packaging may suffer from warpage. FIGS. 1A and 1B illustrate two types of package warpage scenarios. FIG. 1A illustrates dome type warpage where contacts 100 in the center of the lower side of an integrated circuit (IC) chip package 102 are disconnected from corresponding electrical contacts on a printed circuit board (PCB) (not shown) when the center of IC chip package 102 extends upwards to form a dome. Such warpage may occur by thermal contraction of IC chip package 102 during environmental testing. In FIG. 1B, camber type warpage occurs where the edges of chip package 102 bend upward disconnecting contacts 100 near the edges from the corresponding contacts on a printed circuit board. The camber type warpage illustrated in FIG. 1B may be caused by thermal expansion of IC chip package 102 during environmental testing. Although FIGS. 1A and 1B illustrate warpage in a single direction, it is understood that IC chips extend laterally in two directions and that warpage can occur in both directions.
Part of the reliability testing of an IC chip includes functional testing under different temperatures and on special boards, referred to as BIBs (Burn-In-Boards), designed for such functional and environmental testing. Burn-in-Boards include chip sockets that hold the device while the device is stressed in an environmental chamber, and, during application of the environmental stress, the device remains powered and performing desired functional activities. Package warpage resulting from heating and cooling cycles may cause to one or several pins to be disconnected from the socket or to create an unstable contact state. This disconnection may change the stress conditions and can cause over or under stress (current spikes for example) and even destroy the device under test (DUT).
The ability to easily monitor proper device-to-socket connection during stress is important to ensure correct stress conditions and to screen out possible setup-related (false) failures in short time.
Two possible methods to solve at least some of problems associated with testing chips under environmental conditions are:                1. Minimize the warpage occurrence by using high-end sockets that can give better flexibility for warpage (won't monitor the warpage itself, but may minimize the likelihood of occurrence of warpage)—such sockets are very expensive.        2. Monitor the consumed current from the power supply by the BIB—If current level is in desired range, then it is assumed that whole setup is operating correctly and no disconnection occurred. However, monitoring consumed current from the power supply will not identify which pin was disconnected and the resolution of this measurement is low, as one power supply is usually connected to tens of DUTs. Given such a setup, it will not be possible to identify cases where 1 unit was disconnected for short time and reconnected at the same time another unit is disconnected, since the total current will stay the same.        
Another possible solution to detecting electrical disconnection due to chip packaging warpage is to provide a monitoring connection for each pin on the chip. However, such a solution is not feasible especially since the number of pins available on a chip for sensing connections and monitoring connections may be limited. Limiting the number of sensing and monitoring pins or other connections on a chip is a very important design consideration, as the number of I/O pins on a chip is limited and such pins are need for chip I/O functions.
Accordingly, there exists a need for improved methods, systems, and computer readable media for detecting electrical disconnection between IC chip electrical connections and corresponding electrical contacts on a printed circuit board during testing of the chip under environmental conditions.